GitoxideLabs/gitoxide · error

the HEAD pin changed while preparing to attach

Error message

the HEAD pin changed while preparing to attach

What it means

The HEAD pin discovered during `validate_attach` differs from what was remembered: its symbolic target no longer equals the remembered branch name or its commit id differs from the remembered tip. The library bails rather than attach to a branch state that drifted mid-operation. This is a second staleness guard after the HEAD-id check.

Solutions

1. Retry the attach when the repository is quiescent.
2. Identify and stop the concurrent process modifying the branch/HEAD.
3. Re-capture the remembered branch by restarting the flow so the snapshot matches current state.

match attach_reporting(...) {
    Err(e) if e.to_string().contains("HEAD pin changed while preparing") => {
        // restart the whole flow so the remembered snapshot is fresh
        restart_attach_flow()?;
    }
    other => other?,
}

When it happens

Trigger: In attach_reporting/validate_attach: after remembering the branch, the HEAD pin's target name or pin id changed (e.g. a commit was added to the branch, or HEAD was re-pointed to another branch) before validation.

Common situations: Concurrent commits by another tool; an editor auto-fetch/checkout; a background job advancing the branch while the attach was being prepared.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• HEAD changed while preparing to attach
• the remembered branch changed while preparing to attach
• change ID is no longer present in the Tix view
• Tried to use as tree, but was
• Tried to use as commit, but was

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/c219fe3598b5ca43. Report an issue: GitHub.

Appendix: source

Thrown at gix-tix/src/edit/time_travel.rs:517

    }
    Ok(RememberedBranch {
        branch,
        branch_tip: pin.id,
    })
}

fn validate_attach(repository: &gix::Repository, head_id: ObjectId, remembered: &RememberedBranch) -> Result<()> {
    let head = repository.head().context("could not read HEAD before attaching")?;
    if !head.is_detached() || head.id().map(gix::Id::detach) != Some(head_id) {
        anyhow::bail!("HEAD changed while preparing to attach");
    }
    drop(head);
    let pin = history::all_pins(repository)?
        .into_iter()
        .find(history::Pin::is_head)
        .context("the HEAD pin disappeared while preparing to attach")?;
    if pin.target.try_name() != Some(remembered.branch.as_ref()) || pin.id != remembered.branch_tip {
        anyhow::bail!("the HEAD pin changed while preparing to attach");
    }
    let branch_id = repository
        .find_reference(remembered.branch.as_ref())
        .context("the remembered branch disappeared while preparing to attach")?
        .try_id()
        .context("the remembered branch must be a direct reference")?
        .detach();
    if branch_id != remembered.branch_tip {
        anyhow::bail!("the remembered branch changed while preparing to attach");
    }
    ensure_branch_is_available(repository, remembered.branch.as_ref())
}

#[cfg(test)]
pub(crate) fn attach(
    repository_path: &Path,
    bare: bool,
    revisions: &[OsString],

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